Satellite based navigation (Satellite positioning) has become the prerequisite for a wide range of applications. To give examples, automobiles are nowadays very often equipped with global navigation satellite systems (GNSS) such as GPS or Galileo systems to track their routes or to effect payment of road fees. Many people use GNSS when acting outdoors during sports and other activities.
Further to the above, many emerging applications require positioning in deep urban and moderate indoor environments. For example, in emergency situations, it may be required to provide positioning in these difficult to access environments. However, current GPS receivers only provide limited service availability in these environments.
The success of satellite navigation in the mass consumer market such as integration into mobile phones will depend greatly on the service availability in urban canyons and moderate indoor environments. In order to meet these requirements the reception sensitivity of satellite navigation receivers needs to be substantially enhanced.
Attenuation, shadowing, and multipath fading effects in urban canyons and indoor areas frequently degrade the received GPS signal power by 35 dB or more. Therefore improved reception sensitivity is very important for GNSS receivers.